HR: 14:10h
AN: U52B-03    [PDF]
TI: Implications of Multiple Sulfur Isotopes for Biological Systems
AU: * Johnston, D T
EM: dtj@geol.umd.edu
AF: ESSIC and Department of Geology, University of Maryland, College Park, MD 20742 United States
AU: Farquhar, J
EM: jfarquha@essic.umd.edu
AF: ESSIC and Department of Geology, University of Maryland, College Park, MD 20742 United States
AU: Wing, B A
EM: wing@essic.umd.edu
AF: ESSIC and Department of Geology, University of Maryland, College Park, MD 20742 United States
AU: Canfield, D E
EM: dec@biology.umd.edu
AF: DCESS and the Institute of Biology, University of Southern Denmark, Odense, M 5230 Denmark
AU: Habicht, K S
EM: khabicht@biology.sdu.dk
AF: DCESS and the Institute of Biology, University of Southern Denmark, Odense, M 5230 Denmark
AB: The major isotopes of sulfur ($\delta$$^{34}$S) provide a valuable tool to study the evolution and dynamics of ancient biological systems. We recently described the additional information that evidence from $\delta$$^{33}$S and ($\delta$$^{36}$S can provide for our understanding of metabolic pathways in geological environments (Farquhar et al., 2003). The application of the minor isotope system of sulfur arises because recent advances in analytical techniques allow us to measure different mass-dependent fractionation relationships that are predicted for different types of sulfur metabolisms (disproportionation vs. dissimilatory reduction). Here we report on the progress of experiments to measure the mass-dependent fractionation relationships for a variety of sulfur metabolisms and also the implications of our findings for study of the sulfur cycle. Our results may provide a test for a hypothesis that an apparent change in ($\delta$$^{34}$S values during the Neoproterozoic reflected a shift in dominant metabolic process from sulfate reduction to sulfur disproportionation (Canfield and Teske, 1996; Canfield, 2000). This shift in dominant metabolic process has been interpreted as providing evidence for the oxidation state of the ocean and atmosphere at this time.
DE: 0330 Geochemical cycles
DE: 1040 Isotopic composition/chemistry
DE: 1635 Oceans (4203)
SC: U
MN: 2003 Fall Meeting